Sequence contains no matching element ошибка

Well, I’d expect it’s this line that’s throwing the exception:

var documentRow = _dsACL.Documents.First(o => o.ID == id)

First() will throw an exception if it can’t find any matching elements. Given that you’re testing for null immediately afterwards, it sounds like you want FirstOrDefault(), which returns the default value for the element type (which is null for reference types) if no matching items are found:

var documentRow = _dsACL.Documents.FirstOrDefault(o => o.ID == id)

Other options to consider in some situations are Single() (when you believe there’s exactly one matching element) and SingleOrDefault() (when you believe there’s exactly one or zero matching elements). I suspect that FirstOrDefault is the best option in this particular case, but it’s worth knowing about the others anyway.

On the other hand, it looks like you might actually be better off with a join here in the first place. If you didn’t care that it would do all matches (rather than just the first) you could use:

var query = from target in _lstAcl.Documents
            join source in _dsAcl.Document
            where source.ID.ToString() equals target.ID
            select new { source, target };
foreach (var pair in query)
{
    target.Read = source.Read;
    target.ReadRule = source.ReadRule;
    // etc
}

That’s simpler and more efficient IMO.

Even if you do decide to keep the loop, I have a couple of suggestions:

• Get rid of the outer if. You don’t need it, as if Count is zero the for loop body will never execute

• Use exclusive upper bounds in for loops — they’re more idiomatic in C#:

  for (i = 0; i < _lstAcl.Documents.Count; i++)
  

• Eliminate common subexpressions:

  var target = _lstAcl.Documents[i];
  // Now use target for the rest of the loop body
  

• Where possible use foreach instead of for to start with:

  foreach (var target in _lstAcl.Documents)
  

Я использую EF 6.1.0 и создаю службу WCF.

Сначала я создал библиотеку классов, содержащую мои сущности, Mappers и Context для инициализации EF.
Я также создал класс, содержащий экземпляр контекста и имеющий этот код:

public IQueryable<[Entity]> GetAll()
{
    return context.[Entity].AsQueryable();
}

С другой стороны, я создал службу WCF в одном проекте и вызывает функцию GetAll() в файле .svc следующим образом:

public List<[Entity]> GetList()
{
    [iObject] repository = new [Object](new Context());
    return repository.GetAll().ToList();
}

Проект строится. Я даже проверяю cconfiguration, и он находится в правой БД. Однако базы данных и таблиц, которые предположительно созданы, не существует, и появляется сообщение об ошибке «Последовательность не содержит соответствующий элемент».

Если это сбивает с толку, вы можете указать мне ссылку WCF-сервисов с использованием Code First Entity Framework.

Hi

I have a LAB environment set up to test Data Quality Services.

This is the LAB Setup:

• Server: With SQL Server 2012 DB locally installed.  DQS Server Installed.  DQS Client installed.
• Workstation: DQS Client installed only, simulating Data Steward scenario

When CU1 released, I decided to upgrade my LAB to test the performance improvement in DQS.  I proceeded with the following steps:

• Upgrade Server with CU1
• Upgrade DQS Schema on Server
• Upgrade DQS dlls on Server

From the server machine, all DQS functionality seemed to work fine.  On the Workstation machine, I started getting strange errors.  First it complained about parallel processing in a data quality cleansing project.  Maching the threads between
1 and 4 with a sql query made no difference.

I then thought the DQS client must be upgraded but couldn’t find a dqsinstaller.exe file on the workstation.  I then proceeded to run the CU1 setup package on the workstation.  On the Feature page it detected that DQS Client was the only installation
and proceeded with the upgrade without problem.

But the problems on the workstation with DQS client still persists.  If I try the exact same features on the Server, all works.  I can run the cleansing project, I can export matching policy results, no issues at all.

I can’t help but feel a sort of «upgrade» is necessary on the workstation that only has DQS client installed, but I can’t find any information.

Here is what happens:

I have set up a simple Knowledge Base (using a mix of DQS Data and the adventure works 2012 sample db) to check address information (Country, State, City, Address Line 1).

I have also set up a matching policy in the same KB

I use it to try and find «house hold» maches in the address data (i.e. two or more people live at the same address).

When I run a data quality project using the matching policy, on the data in the AdventureWorks 2012 sample database using the Person.address (and related tables) the project completes successfully.

However, when I try to export the result to a SQL table, I get the following error:

2012/05/30 05:04:26 PM|[]|1|INFO|PUID|Microsoft.Ssdqs.Proxy.EntryPoint.ProxyInit|Starting DQS ProxyInit: version [11.0.2316.0], machine name [WS1], user name [LABbaileym], operating system [Microsoft Windows NT 6.1.7601 Service Pack 1]…
2012/05/30 05:04:26 PM|[]|1|INFO|PUID|Microsoft.Ssdqs.Proxy.EntryPoint.ProxyInit|DQS ProxyInit started.
2012/05/30 05:04:50 PM|[]|1|ERROR|CLIENT|Microsoft.Ssdqs.Studio.ViewModels.Utilities.UIHelper|An error has occurred.
System.InvalidOperationException:Sequence contains no matching element;
   at System.Linq.Enumerable.First[TSource](IEnumerable`1 source, Func`2 predicate);
   at Microsoft.Ssdqs.Studio.ViewModels.Data.DataSources.DatabaseHelper.GetStagingDatabase();
   at Microsoft.Ssdqs.Studio.ViewModels.ViewModels.Matching.MatchingExportViewModel.CreateTemporaryRepositoryMetadata(RepositoryMetadata source);
   at Microsoft.Ssdqs.Studio.ViewModels.ViewModels.Matching.MatchingExportViewModel.ExportMatchingContentCommandExecute(Object parameter);
   at Microsoft.Ssdqs.Studio.ViewModels.Utilities.UICommand.Execute(Object parameter);
   at Microsoft.Ssdqs.Studio.Views.Pages.Matching.MatchingExportView.MatchingExportExecute(Object sender, ExecutedRoutedEventArgs e);
   at System.Windows.Input.CommandBinding.OnExecuted(Object sender, ExecutedRoutedEventArgs e);
   at System.Windows.Input.CommandManager.ExecuteCommandBinding(Object sender, ExecutedRoutedEventArgs e, CommandBinding commandBinding);
   at System.Windows.Input.CommandManager.FindCommandBinding(CommandBindingCollection commandBindings, Object sender, RoutedEventArgs e, ICommand command, Boolean execute);
   at System.Windows.Input.CommandManager.FindCommandBinding(Object sender, RoutedEventArgs e, ICommand command, Boolean execute);
   at System.Windows.Input.CommandManager.OnExecuted(Object sender, ExecutedRoutedEventArgs e);
   at System.Windows.UIElement.OnExecutedThunk(Object sender, ExecutedRoutedEventArgs e);
   at System.Windows.Input.ExecutedRoutedEventArgs.InvokeEventHandler(Delegate genericHandler, Object target);
   at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target);
   at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs);
   at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised);
   at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args);
   at System.Windows.UIElement.RaiseEvent(RoutedEventArgs args, Boolean trusted);
   at System.Windows.Input.RoutedCommand.ExecuteImpl(Object parameter, IInputElement target, Boolean userInitiated);
   at System.Windows.Input.RoutedCommand.ExecuteCore(Object parameter, IInputElement target, Boolean userInitiated);
   at MS.Internal.Commands.CommandHelpers.CriticalExecuteCommandSource(ICommandSource commandSource, Boolean userInitiated);
   at System.Windows.Controls.Primitives.ButtonBase.OnClick();
   at System.Windows.Controls.Button.OnClick();
   at System.Windows.Controls.Primitives.ButtonBase.OnMouseLeftButtonUp(MouseButtonEventArgs e);
   at System.Windows.UIElement.OnMouseLeftButtonUpThunk(Object sender, MouseButtonEventArgs e);
   at System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget);
   at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target);
   at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs);
   at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised);
   at System.Windows.UIElement.ReRaiseEventAs(DependencyObject sender, RoutedEventArgs args, RoutedEvent newEvent);
   at System.Windows.UIElement.OnMouseUpThunk(Object sender, MouseButtonEventArgs e);
   at System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget);
   at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target);
   at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs);
   at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised);
   at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args);
   at System.Windows.UIElement.RaiseTrustedEvent(RoutedEventArgs args);
   at System.Windows.UIElement.RaiseEvent(RoutedEventArgs args, Boolean trusted);
   at System.Windows.Input.InputManager.ProcessStagingArea();
   at System.Windows.Input.InputManager.ProcessInput(InputEventArgs input);
   at System.Windows.Input.InputProviderSite.ReportInput(InputReport inputReport);
   at System.Windows.Interop.HwndMouseInputProvider.ReportInput(IntPtr hwnd, InputMode mode, Int32 timestamp, RawMouseActions actions, Int32 x, Int32 y, Int32 wheel);
   at System.Windows.Interop.HwndMouseInputProvider.FilterMessage(IntPtr hwnd, WindowMessage msg, IntPtr wParam, IntPtr lParam, Boolean& handled);
   at System.Windows.Interop.HwndSource.InputFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled);
   at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled);
   at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o);
   at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs);
   at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler)

I doubt that it has anything to do with security seeing as before the CU1 on the server, I could export results from this workstation to that database.

Any advice would be appreciated.

Thanks

Michelle

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